## Applying Parametric Estimates

Quantitatively based durations use mathematical formulas to predict how long an activity will take based on the "quantities" of work to be completed. For example, a commercial printer needs to print 100,000 brochures. The workers include two pressmen and two bindery experts to fold and package the brochures. Notice how the duration is how long the activity will take to complete, while the effort is the total number of hours (labor) invested because of the resources involved. The decomposed work, with quantitative factors, is shown in Table 6-1.

EXAM TIP Duration is how long an activity takes, while effort is the billable time for the labor to complete the activity. Consider an activity that is scheduled to last 40 hours. The project manager must consider the cost of the person's time assigned to complete the project work—for example, a senior full-time engineer versus a part-time person—at a lower cost. The senior engineer may be able to complete the activity in 40 consecutive work hours, but the cost of this employee's time may be more than the value of the activity. The part-time employee may be able to complete the task in two segments of 20 hours, but her time is billed at a substantially lower rate.